Patent ductus arteriosus (PDA) is a congenital malformation characterized by the failure of closure of the ductus arteriosus, a fetal vascular structure connecting the pulmonary artery to the descending aorta. In healthy newborns, the ductus closes spontaneously within the first hours or days of life. If it remains patent, it allows abnormal passage of oxygenated blood from the aorta to the pulmonary circulation, resulting in a left-to-right shunt. This condition causes volume overload of the left heart chambers and lungs, with a risk of complications if left untreated.
Patent ductus arteriosus accounts for about 5–10% of congenital heart diseases, with a higher prevalence in preterm infants. In full-term newborns, the estimated prevalence is approximately 1 case per 2,000 live births, while in preterm infants weighing less than 1000 g, it can reach up to 30–60%.
Physiological closure of the ductus arteriosus normally occurs through two mechanisms: functional contraction of the ductal smooth muscle cells mediated by increased arterial pressure and decreased prostaglandin levels, followed by anatomical remodeling with fibrous obliteration. Disruption of these processes can lead to patent ductus arteriosus.
The main causes of PDA include:
Some maternal medications, such as prostaglandin inhibitors (e.g., NSAIDs) taken during late pregnancy, may affect the fate of the ductus arteriosus, but they more often induce premature closure rather than persistence.
In the fetus, the ductus arteriosus is a vital structure that allows blood to bypass the non-functioning lungs. At birth, with the onset of respiration, the rapid increase in systemic arterial pressure and the decrease in pulmonary vascular resistance trigger functional closure of the ductus. If this process fails, oxygenated blood from the aorta flows into the pulmonary artery, creating a left-to-right shunt.
Persistent shunting leads to:
The severity of the hemodynamic impact primarily depends on the ductus diameter and the pressure difference between the aorta and the pulmonary artery. Small ducts may be hemodynamically insignificant, while large ducts can rapidly cause congestive heart failure and hypoxia.
Patent ductus arteriosus is a congenital condition favored by several well-recognized risk factors. Although it often occurs sporadically, certain conditions significantly increase its likelihood.
Main predisposing factors include:
Primary prevention focuses on optimal pregnancy management, prevention of congenital infections (particularly rubella vaccination), and careful neonatal care, especially in preterm infants. Nevertheless, despite preventive strategies, many cases of PDA occur without identifiable modifiable causes.
The clinical presentation of patent ductus arteriosus varies widely based on the duct size and shunt extent. Small PDAs may remain asymptomatic throughout life, whereas large ducts cause symptoms within the first weeks of life.
In neonates and infants with hemodynamically significant PDA, history may reveal:
In adults with a small untreated PDA, the condition may be discovered incidentally or manifest with symptoms such as fatigue, exertional dyspnea, or infectious endocarditis.
Physical examination in patients with significant PDA typically reveals a continuous murmur ("machinery murmur") best heard in the left infraclavicular region, persisting throughout systole and diastole. This murmur originates from the continuous blood flow through the duct, maintained by the persistent pressure gradient between the aorta and pulmonary artery.
Additional clinical findings may include:
Clinical suspicion of PDA should arise in the presence of a characteristic continuous murmur associated with signs of hemodynamic overload, especially in neonates and preterm infants. A widened pulse pressure is an additional suggestive clue.
Transthoracic echocardiography with Doppler imaging is the reference investigation. It allows direct visualization of the ductus, documentation of the shunt flow, and assessment of the degree of left heart chamber overload. Color Doppler imaging shows continuous turbulent flow from the aorta into the pulmonary artery.
In preterm neonates, serial echocardiographic monitoring is often used to follow the evolution of the duct and guide therapeutic decisions.
In selected cases, cardiac magnetic resonance imaging (MRI) provides detailed assessment of ventricular volumes and shunt flow. Cardiac catheterization is now rarely needed for diagnosis but can be employed in particular contexts, for example prior to percutaneous closure in older patients.
The logical sequence includes: clinical suspicion based on continuous murmur and signs of volume overload; confirmation by transthoracic echocardiography; possible further investigation with advanced imaging methods in complex cases or before therapeutic intervention.
The management of patent ductus arteriosus depends on the patient's age, ductus size, and degree of hemodynamic compromise. In preterm neonates, treatment aims to prevent complications from pulmonary hypervolemia and heart failure, while in older children and adults, the goal is to prevent pulmonary hypertension and infectious endocarditis.
The therapeutic options include:
In preterm neonates, initial closure attempts involve the administration of prostaglandin inhibitors (indomethacin or ibuprofen). These drugs promote ductal contraction and functional closure. Recently, paracetamol has been explored as a potential alternative with a favorable safety profile.
Pharmacological treatment is less effective in term neonates and older children, where interventional closure is generally preferred.
Percutaneous closure using occluding devices is now the treatment of choice for most patients with hemodynamically significant PDA. The procedure is performed under general anesthesia or conscious sedation, via femoral venous access, with device deployment across the duct.
Success rates are high, exceeding 95%, with a low complication rate.
Surgical closure via ligation or division of the ductus is reserved for cases where percutaneous intervention is not feasible, such as in very small neonates or ducts with complex anatomy. Surgery is usually performed through a left thoracotomy, with excellent long-term results.
The prognosis for patients undergoing early closure of patent ductus arteriosus is excellent. Children treated within the first months of life show complete normalization of cardiac hemodynamics, with no impact on quality of life or life expectancy.
In untreated cases, the risk of complications progressively increases with age, especially due to the development of pulmonary hypertension, heart failure, and endovascular infections.
The main complications associated with untreated patent ductus arteriosus include:
Early diagnosis and timely management are essential to prevent these severe complications and ensure an optimal prognosis.